Examining the efficiency of muffle furnace-induced alkaline hydrolysis in determining the titanium content of environmental samples containing engineered titanium dioxide particles

Abstract

A novel muffle furnace (MF)-based potassium hydroxide (KOH) fusion digestion technique was developed and evaluated for different titanium dioxide materials in various solid matrices. Digestion of different environmental samples containing sediments, clay minerals and humic acid with and without TiO(2) particles was first performed utilizing the MF-based KOH fusion technique and its dissolution efficacy was compared to a Bunsen burner (BB)-based KOH fusion method. The three types of TiO(2) particles (anatase, brookite and rutile) were then digested with the KOH fusion techniques and microwave (MW)-based nitric (HNO3)–hydrofluoric (HF) mixed acid digestion methods. Statistical analysis of the results revealed that Ti recoveries were comparable for the KOH fusion methods (BB and MF). For pure TiO(2) particles, the measured Ti recoveries compared to calculated values were 96%, 85% and 87% for anatase, brookite and rutile TiO(2) materials, respectively, by the MF-based fusion technique. These recoveries were consistent and less variable than the BB-based fusion technique recoveries of 104%, 97% and 72% and MW-based HNO3–HF mixed acids digestion recoveries of 80%, 81% and 14%, respectively, for anatase, brookite and rutile. Ti percent recoveries and measurement precision decreased for both the BB and MF methods when TiO(2) was spiked into sediment, clay minerals, and humic acid. This drop in efficacy was counteracted by more thorough homogenization of the spiked mixtures and by increasing the mass of KOH in the MF fusion process from 1.6 g to 10.0 g. The MF-based fusion technique is consistently superior in digestion efficiency for all three TiO(2) polymorphs. The MF-based fusion technique required 20 minutes for digestion of 25 samples (based on in-house Lindberg MF capacity) compared to 8 hours for the same number of samples using the BB-based fusion technique. Thus, the MF-based fusion technique can be used to dissolve a large number of samples in a shorter time (e.g., 500 samples per 8 hours) while conserving energy and eliminating health and safety risks from methods involving HF.

Spectroscopic Characterization of TiO2 Polymorphs in Wastewater Treatment and Sediment Samples

“…The sediments were further ground using an agate pestle mortar and mounted on Kapton tape for XANES analysis. The Ti contents in the NSWRP samples and the NSC sediments were analyzed using muffle furnace-induced alkaline hydrolysis followed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) (Vista MPX ICP Spectrometer, Varian), according to the methods by Silva et al 35 To estimate the amount of TiO 2 entering the NSWRP, four influent samples were collected and analyzed during the two-month sampling period. The Ti recoveries were 88 ± 3 and 90 ± 3% for anatase and rutile, respectively, when 0.1 g of TiO 2 was spiked into 0.25 g of NSC sediments.…”

2013 Atomic spectrometry update—A review of advances in environmental analysis

“…The determination of Ti in environmental studies is gaining importance as a means of estimating concentrations of engineered TiO 2 nanoparticles in the environment. In the analysis of a range of materials 152 (stream sediment, bentonite, kaolinite and humic acid spiked with anatase, brookite and rutile), a novel muffle-furnace-based KOH fusion method yielded much higher Ti recoveries than microwave-assisted digestion. For example, results obtained when Method EPA 3051A was applied to pure samples of the TiO 2 polymorphs were <10% of theoretical values, whilst recoveries of ca.…”

“…Normally, the determination of 143 Nd/ 144 Nd and 147 Sm/ 144 Nd ratios by TIMS requires puried Nd and Sm fractions to be loaded onto different laments because of severe isobaric interferences, making the procedure lengthy and laborious. Li et al 309 proposed a new method, using a mixed 152 Sm- 148 Nd spike rather than the traditional 149 Sm-150 Nd spike, in which both ratios and concentrations of Nd and Sm were measured simultaneously on the same lament loading. Measurements of ten silicate rock CRMs conrmed that neither precision nor accuracy of the results had been compromised.…”